It's an excellent question. I would love to see a third party blind review study of the efficacy of the machines. I would like to see controlled experiments using the machines. It's very difficult to do because the technology of course is patented and owned, and a single company has a monopoly on the machines used in Canadian prisons. Like other manufacturers of technology, they are, I think, reluctant to subject their technology to third party review.
CSC will quote that the manufacturer says that the incidence of false positives is less than 0.1%, but when I asked them last year in an access to information request about the reliability factor, they said that CSC does not possess documentation concerning the reliability of the IONSCAN machines. They quoted me the manufacturer's response, and it appears that they have collected no independent data on the machines.